has part has part Duplication of the 1st metacarpal 2009-01-29T03:33:31Z Partail or complete duplication of the first metacarpal bone. In contrast to the metacarpals 2-5, the first metacarpal is embryologically of phalangeal origin. This term applies if the first metacarpal is completely or partially duplicated. Depending on the severity, the appearance on x-ray can vary from a notched metacarpal (the duplicated bone is almost completely fused with the metacarpal), a partially fused appearance of the two bones (in most cases the fused bone resembles a Y-shape), or two separate metacarpal bones appearing side to side. HP:0009609 Partial/complete duplication of the 1st metacarpal UMLS:C4021426 Partial/complete duplication of the 1st long bone of hand Complete duplication of the first metacarpal Bifid first metacarpal Duplication of the proximal phalanx of hand Abnormal 1st metacarpal morphology